[meteorite-list] Comet Schwassmann-Wachmann 3's Breakup Near Earth Offers Viewing Spectacle

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri May 5 12:30:19 2006
Message-ID: <200605051628.JAA29898_at_zagami.jpl.nasa.gov>

http://www.baltimoresun.com/news/health/bal-hs.comet05may05,0,7176805.story

Comet's breakup near Earth offers viewing spectacle
By Frank D. Roylance
Baltimore Sun
May 5, 2006

Astronomers will have a ringside seat during the coming weeks as a dying
comet with a tongue-twisting name flies past the Earth and literally
falls apart in front of their eyes.

Comet 73P/Schwassmann-Wachmann 3 is buzzing the Earth -- closer than any
comet in 23 years. It's gliding by as close as 5.5 million miles away,
barely 20 times the moon's distance from the Earth.

Even better for scientists, SW3's icy nucleus is coming undone like the
seeds of a dandelion in a stiff wind, revealing the physical and
chemical secrets of its interior.

Astronomers have counted at least 59 fragments already, and there's no
end in sight.

"It's driving us nuts; fragments of fragments of fragments," said Don
Yeomans, manager of NASA's Near Earth Objects Program office at the Jet
Propulsion Laboratory in Pasadena, Calif. It is his job to keep track of
them all and tell astronomers where to find them.

"It's doing its best to make our lives miserable," he said, laughing.

As near as it is coming in astronomical terms, scientists insist there
is no danger that SW3 will collide with the Earth, although its debris
may produce a small meteor shower years from now.

The comet's fragments are too small to produce a naked-eye spectacle,
like comets Hyakutake in 1996 and Hale-Bopp in 1997. But one or two may
be visible in the eastern sky for the next two weeks. You will need
binoculars and a dark location.

Look in the late evening. The comet is moving through the "Summer
Triangle," formed by the bright stars Vega, Altair and Deneb. It will
drop closer to the eastern horizon each night.

Many amateurs are already watching the comet's bust-up through backyard
telescopes.

"I was able to hit it right away," said Tim Hickman, 60, who first
photographed the comet's largest fragment April 15 from his backyard in
Timonium. "It's kind of cool to see one breaking up, the end of the life
of a comet. It looked like a miniature comet, with a little head and a
little tail."

During several hours at his eyepiece, he said, "I could actually see its
motion relative to the stars." But it's been too faint to see with the
naked eye.

Hal Weaver, a planetary astronomer at the Johns Hopkins University
Applied Physics Laboratory, had this advice: "The next two weeks is when
it's going to be brightest. People should get out there with their
binoculars."

Weaver has been leading a Hubble Space Telescope team watching the comet
break apart. But he also plans to try to see SW3 with his own eyes. Why?

"My gosh, this thing is breaking apart," he said. "Maybe it's the last
time people will be able to see it. You can say you were there."

The comet was discovered in 1930 by the German astronomers Arnold
Schwassmann and Arno Arthur Wachmann. Subsequent calculations revealed
that it circles once every 5 1/2 years between the sun and the orbit of
Jupiter. But it wasn't seen again until 1979. Astronomers missed it in
1985, but found it again in 1990.

On its 1995 return, SW3 startled everyone, Weaver said. "It got
dramatically brighter in a short period of time, and shortly after that
people started seeing more than one nucleus."

The comet -- a hunk of ice and dust that astronomers estimate was once 1
to 3 miles long, had broken apart. Now they had four fragments -- A, B,
C and D.

Only two were spotted on the comet's return in 2000. But astronomers had
to peer all the way across the solar system to see it at all.

Weaver applied for observation time on Hubble to watch the comet's 2006
return, hoping that SW3's fragment C had survived.
Received on Fri 05 May 2006 12:28:13 PM PDT